Radio frequency switch circuit

Abstract

The present application provides a kind of radio frequency switch circuit, comprising: N series stacked radio frequency switch unit circuit, wherein N is the integer greater than 1, control circuit is configured to provide control voltage to radio frequency switch unit circuit, to make it in different operating states, wherein the radio frequency switch unit circuit includes the first switch branch, the second switch branch and the third switch branch connected in parallel, the first switch branch is configured as main radio frequency passage, the second switch branch is configured as forward voltage compensation circuit, and the third switch branch is configured as reverse voltage compensation circuit.

Description

Technical Field

[0001] This invention relates to radio frequency integrated circuits, and more specifically, to a radio frequency switching circuit. Background Technology

[0002] A radio frequency (RF) switching circuit is a circuit used in wireless communication systems to switch signal transmission paths between multiple antennas and a single RF receiver or transmitter. An RF switching circuit typically consists of an RF switching branch circuit and a switch control circuit. The RF switching branch circuit connects or isolates the input and output ports of different antennas, thereby controlling the signal flow path. The switch control circuit controls the operating state of the RF switching unit circuit to achieve seamless switching between antennas, thus optimizing the performance of the wireless communication system. Depending on the application, RF switching circuits can be categorized into transmit switching circuits, receive switching circuits, antenna tuning switching circuits, etc.

[0003] Currently, the RF switch circuit chips widely used in mobile terminals mainly employ CMOS SOI (Silicon-On-Insulator) technology, hereinafter referred to as SOI RF switch circuits. SOI RF switch circuits are RF switch circuits based on silicon-on-insulator (SOI) technology, featuring low insertion loss, high isolation, and fast switching speed. SOI RF switch circuits are widely used in antenna aperture tuning, enabling multi-band tuning and bandwidth enhancement of the antenna. The application of SOI RF switch circuits in antenna aperture tuning typically involves adding tunable components, such as tunable capacitors or inductors, to the antenna, and then using SOI RF switch circuits to control the switching states of these components. By changing the capacitance or inductance value of the tunable component, multi-band tuning and bandwidth enhancement of the antenna can be achieved. Specifically, SOI RF switch circuits are commonly used to achieve multi-band tuning of a single antenna. In this case, a tunable capacitor or inductor is added to the antenna, and by controlling the switching state of the SOI RF switch circuit, the capacitance or inductance value of the tunable component can be changed, thereby achieving multi-band tuning of the antenna. For example, in an LTE tri-band antenna system, the SOI RF switch circuit can control three tunable elements to achieve tuning and bandwidth enhancement across the high, medium, and low frequency bands. In summary, the SOI RF switch circuit has wide applications in antenna aperture tuning, enabling multi-band tuning and bandwidth enhancement of the antenna.

[0004] In existing technologies, RF antenna tuning switch circuit chips are typically implemented using CMOS SOI technology. The switch is controlled by positive and negative voltages; when the switch is on, a positive voltage is applied to the transistor gate, and when the switch is off, a negative voltage is applied. Key performance indicators for RF antenna switch circuits include insertion loss, isolation, harmonics, power handling capability, and voltage withstand capability. For antenna tuning switches, since they connect to the antenna port, there are strict requirements for voltage withstand capability. Depending on the connection location of the antenna tuning switch, different voltage levels such as 45V, 60V, and 80V are available. In actual product design, different models of RF switch chips are designed based on different voltage withstand values. The breakdown voltage (BV_fet) of a single transistor in CMOS SOI technology is generally less than 3.5V. To withstand the RF voltage signal swing under maximum transmit power conditions, CMOS SOI antenna tuning switch circuits generally use a design of multiple transistors stacked in series, such as... Figure 1 As shown. Figure 1 This diagram shows a circuit schematic of an N-stage stacked RF switch branch. The withstand voltage of the RF switch circuit depends on the voltage withstand capability of the off-state branch. By increasing the number of stacked transistor stages in the off-state switch branch, the power withstand capability, i.e., the withstand voltage capability, of the off-state branch can be improved. Generally, N=14 stacked cascades can withstand 45V, N=20 stacked cascades can withstand 60V, and N=26 stacked cascades can withstand 80V.

[0005] The breakdown voltage of a single transistor in the off state is defined as VB_fet. Theoretically, if n transistors are stacked in series, the total breakdown voltage BV is as shown in Formula 1 below:

[0006] BV = n × VB_fet (1)

[0007] In fact, due to the parasitic capacitance of the transistor to ground, the equivalent circuit of the switching branch in the off state is as follows: Figure 2 As shown. Figure 2 This diagram illustrates the equivalent circuit of an N-stage series-stacked RF switch branch in the off-isolation state. The presence of parasitic capacitance results in uneven voltage distribution among the stacked transistors. From the signal input to GND, the voltage drop across each transistor gradually decreases, with the largest voltage drop observed at the signal input. This limits the total breakdown voltage of the stacked transistor switch branch. The total breakdown voltage BV of n series-stacked transistors is shown in Equation 2 below:

[0008]

[0009] Where Cds is the source-drain equivalent capacitance of the transistor, Cgnd is the transistor's capacitance to ground, and α is determined by the following formulas 3 and 4:

[0010]

[0011]

[0012] Figure 3 This is a schematic diagram of the breakdown voltage BV versus the number of stacks, based on Formulas 1 and 2. (Reference) Figure 3 Once the number of stacked components reaches a certain level, the breakdown voltage BV of the switching branch will no longer increase, but will instead reach a saturation state.

[0013] To address the aforementioned issues, the Cds capacitance value of each transistor stage is compensated, ensuring that the equivalent Cds value of each stage is equal, thereby further improving the withstand voltage of the switching branch. This design guarantees uniform voltage swing for each transistor. For example, when… Figure 1 When the D terminal is connected to the antenna signal terminal and the S terminal is connected to GND, by optimizing the size of each stage of the transistor, the size of each stage of the transistor decreases in a gradient from the D port to the S port. This allows the voltage swing VDS of each stage of the transistor to be uniform when viewed from the D terminal to the S terminal in the off state. Figure 4 This is a schematic diagram showing the voltage swing VDS of each transistor stage after compensation for the Cds capacitance value. (Reference) Figure 4 As shown, after compensation, the transistor voltage swing VDS of each stage is uniform.

[0014] According to the above method, by optimizing the size of each stage transistor, a radio frequency switching circuit with high voltage withstand capability can be obtained. However, a drawback of the above technical solution is that Cds compensation can only be performed in one direction. If the directions of the S and D terminals are reversed, that is, the S terminal is connected to the antenna signal terminal and the D terminal is grounded, then the voltage swing VDS of each stage transistor will become non-uniform, with the voltage swing of the transistor near the signal terminal being larger and the signal swing of the transistor near the GND terminal being smaller. Figure 5 This is a schematic diagram showing the voltage swing VDS of each transistor stage after reverse compensation of the Cds capacitance value. (Reference) Figure 5 As shown, the transistor voltage swing VDS becomes non-uniform in each stage. This design of the RF switch circuit will cause regional saturation after the breakdown voltage BV reaches a certain value, i.e., the conditions shown in Equation 2 above will occur. Figure 3 The situation described.

[0015] The voltage compensation scheme for the aforementioned RF switch circuit can only perform unidirectional compensation. In fact, antenna tuning switches have multiple applications. Taking the single-pole four-throw SP4T switch as an example... Figure 6This diagram illustrates the first application scenario of the antenna tuning switch circuit. In this scenario, the ANT port of the SP4T is connected to the antenna, and the withstand voltage compensation design of the RF switch circuit compensates from the D terminal to the S terminal. Figure 7 This diagram illustrates a second application scenario for the antenna tuning switch circuit. In this scenario, the ANT port of the SP4T antenna is grounded, and the voltage compensation design of the RF switch circuit compensates from the S terminal to the D terminal. Due to the different compensation direction, two types of chips are generally required, referred to as SP4T and 4XSPST respectively. Summary of the Invention

[0016] This invention provides an RF switch circuit that enables bidirectional withstand voltage compensation for the RF switch branch. The withstand voltage value of the RF switch circuit remains the same in both forward and reverse compensation application scenarios. The antenna tuning switch circuit using this invention can be used as an SP4T or a 4XSPST, enabling a single product to be adapted to various antenna tuning applications, thereby further optimizing the mobile terminal's Bill of Materials (BOM) and cost.

[0017] One aspect of the present invention provides a radio frequency (RF) switch circuit, comprising: N RF switch unit circuits stacked in series, where N is an integer greater than 1; and a control circuit configured to provide a control voltage to the RF switch unit circuits to place them in different operating states. The RF switch unit circuits include a first switch branch, a second switch branch, and a third switch branch connected in parallel. The first switch branch is configured as a main RF path, the second switch branch is configured as a forward withstand voltage compensation circuit, and the third switch branch is configured as a reverse withstand voltage compensation circuit.

[0018] One aspect of the present invention provides a radio frequency (RF) switch circuit, wherein the first switch branch includes a first transistor, the first transistor being configured such that its gate is connected to a first control port of the RF switch unit circuit, its drain is connected to a first output port of the RF switch unit circuit, and its source is connected to a second output port of the RF switch unit circuit.

[0019] One aspect of the present invention provides a radio frequency (RF) switch circuit, wherein the second switch branch includes a first compensation transistor and a first switch transistor, the first compensation transistor being configured such that its gate is connected to a second control port of the RF switch unit circuit, its drain is connected to a first output port of the RF switch unit circuit, and its source is connected to the drain of the first switch transistor; the first switch transistor being configured such that its gate is connected to a third control port of the RF switch unit circuit, and its source is connected to a second output port of the RF switch unit circuit.

[0020] One aspect of the present invention provides a radio frequency switching circuit, wherein the size of the first compensation transistor is configured to be larger than the size of the first switching transistor.

[0021] One aspect of the present invention provides a radio frequency (RF) switch circuit, wherein the third switch branch includes a second compensation transistor and a second switch transistor, the second compensation transistor being configured such that its gate is connected to a fourth control port of the RF switch unit circuit, its drain is connected to a first output port of the RF switch unit circuit, and its source is connected to the drain of the second switch transistor; the second switch transistor being configured such that its gate is connected to a fifth control port of the RF switch unit circuit, and its source is connected to a second output port of the RF switch unit circuit.

[0022] One aspect of the present invention provides a radio frequency switching circuit in which the size of the second compensation transistor is configured to be larger than the size of the second switching transistor.

[0023] One aspect of the present invention provides a radio frequency switch circuit, wherein the control circuit is configured to control the radio frequency switch unit control circuit to put it into an on state, a first isolation state, or a second isolation state.

[0024] One aspect of the present invention provides a radio frequency switching circuit, wherein, in the on state, the control circuit provides an on-state voltage to a first transistor in a first switching branch; provides an on-state voltage to a first compensation transistor and a first switching transistor in a second switching branch; and provides an on-state voltage to a second compensation transistor and a second switching transistor in a third switching branch.

[0025] One aspect of the present invention provides a radio frequency switching circuit, wherein, in a first isolation state, the control circuit provides a turn-off voltage to a first transistor in a first switching branch; provides a turn-off voltage to a first compensation transistor in a second switching branch and a turn-on voltage to the first switching transistor; and provides a turn-on voltage to a second compensation transistor in a third switching branch and a turn-off voltage to the second switching transistor.

[0026] One aspect of the present invention provides a radio frequency switching circuit, wherein, in a second isolation state, the control circuit provides a turn-off voltage to a first transistor in a first switching branch; provides an on-state voltage to a first compensation transistor in a second switching branch and a turn-off voltage to the first switching transistor; and provides a turn-off voltage to a second compensation transistor in a third switching branch and an on-state voltage to the second switching transistor. Attached Figure Description

[0027] Figure 1This is a circuit diagram showing an N-stage stacked RF switch branch;

[0028] Figure 2 This is a schematic diagram showing the equivalent circuit of an N-stage series-stacked RF switch branch in the off-isolation state;

[0029] Figure 3 It is a schematic diagram of the breakdown voltage BV versus the number of stacks based on Formulas 1 and 2.

[0030] Figure 4 This is a schematic diagram showing the voltage swing VDS of each stage transistor after compensation of the Cds capacitance value of the transistor.

[0031] Figure 5 This is a schematic diagram of the voltage swing VDS of each stage transistor after reverse compensation of the Cds capacitance value of the transistor.

[0032] Figure 6 This is a schematic diagram illustrating the first application scenario of the antenna tuning switch circuit;

[0033] Figure 7 This is a schematic diagram illustrating a second application scenario of the antenna tuning switch circuit;

[0034] Figure 8 This is a schematic diagram of a radio frequency switch circuit according to an embodiment of the present invention;

[0035] Figure 9 This is a schematic diagram of a standard transistor switching unit circuit designed using CMOS SOI technology according to an embodiment of the present invention;

[0036] Figure 10 This is a schematic diagram of the equivalent circuit showing the conduction state of a transistor switching unit circuit;

[0037] Figure 11 This is a schematic diagram showing the equivalent circuit of the transistor switching unit circuit in the off state;

[0038] Figure 12 This is a schematic diagram showing the equivalent circuit diagram of the radio frequency switch unit circuit in isolation state 1 according to an embodiment of the present invention;

[0039] Figure 13 This is a schematic diagram of an application scenario of a radio frequency switch circuit according to an embodiment of the present invention;

[0040] Figure 14 This is a schematic diagram showing the equivalent circuit of the forward withstand voltage compensation of a two-stage stacked radio frequency switch circuit according to an embodiment of the present invention;

[0041] Figure 15This is a schematic diagram showing the equivalent circuit of reverse withstand voltage compensation for a two-stage stacked radio frequency switch circuit according to an embodiment of the present invention.

[0042] Figure 16 This is a schematic diagram illustrating the structure of a radio frequency switching circuit according to an embodiment of the present invention; and

[0043] Figure 17 This is a schematic diagram illustrating a radio frequency switch system according to an embodiment of the present invention. Detailed Implementation

[0044] Before proceeding with the detailed description below, it may be advantageous to define certain words and phrases used throughout this patent document. The terms “coupled,” “connected,” and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are physically in contact with each other. The terms “transmit,” “receive,” and “communicate,” and their derivatives cover both direct and indirect communication. The terms “comprise,” “include,” and their derivatives refer to, but are not limited to, those including, those including, those including, those including. The term “or” is inclusive, meaning and / or. The phrase “associated with,” and its derivatives refer to, including, being contained within, interconnected, containing, being included in, being connected or connected to, coupled or coupled to, communicating with, cooperating, intertwining, juxtaposed, proximate, bound or bound to, having, having attributes, having a relationship or being related to, etc. The term “controller” refers to any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware, or a combination of hardware and software and / or firmware. The functionality associated with any particular controller may be centralized or distributed, local or remote. The phrase "at least one" when used with a list of items means that different combinations of one or more of the listed items may be used, and that only one item from the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0045] Definitions of other specific words and phrases are provided throughout this patent document. Those skilled in the art will understand that, in many, if not most, cases, such definitions apply to the prior and future use of the words and phrases thus defined.

[0046] In this patent document, the application combination of modules and the hierarchical division of sub-modules are for illustrative purposes only. Without departing from the scope of this disclosure, the application combination of modules and the hierarchical division of sub-modules can be in different ways.

[0047] Figure 8 This is a schematic diagram of a radio frequency switch circuit according to an embodiment of the present invention.

[0048] refer to Figure 8 This invention provides a radio frequency (RF) switch circuit, which is formed by stacking N RF switch unit circuits in series, where N is an integer greater than 1. The RF switch unit circuit includes a first switch branch, a second switch branch, and a third switch branch, which are connected in parallel. The first switch branch is composed of transistor M1, with the drain of transistor M1 connected to port P1, the source of transistor M1 connected to port P2, and the gate of transistor M1 connected to port G1. The second switch branch is composed of transistors M2A and M2B, with the drain of transistor M2A connected to port P1, the source of transistor M2A connected to the drain of transistor M2B, the source of transistor M2B connected to port P2, the gate of transistor M2A connected to port G2A, and the gate of transistor M2B connected to port G2B. The third switching branch consists of transistors M3A and M3B. The drain of transistor M3A is connected to port P1, the source of transistor M3A is connected to the drain of transistor M3B, the source of transistor M3B is connected to port P2, the gate of transistor M3A is connected to port G3A, and the gate of transistor M3B is connected to port G2B. The first switching branch is the main RF path. The size of transistor M1 is determined according to the actual application scenario. When the forward direction is defined as from P1 to P2, the RF signal is seen from P1, and P2 is grounded. When the reverse direction is defined as from P2 to P1, the RF signal is seen from P2, and P1 is grounded. The second switching branch serves as a forward withstand voltage compensation circuit, i.e., the RF swing of the antenna signal is seen from the drain of M1. M2A is a compensation transistor, smaller than M1, and transistor M2B is used to control the opening and closing of the second branch, also smaller than M2A. The third switching branch serves as a reverse withstand voltage compensation circuit, meaning it displays the RF swing of the antenna signal from the source terminal of M1. M3A is a compensation transistor, smaller than M1, and transistor M3B controls the switching on and off of the third branch; its size is also smaller than M3A. By connecting these RF switching units in series, an N-level stacked structure is formed, where N is an integer greater than 1, such as... Figure 16 As shown. Figure 16 This is a schematic diagram illustrating the structure of a radio frequency (RF) switch circuit according to an embodiment of the present invention. By configuring different gate control voltages, the above-described RF switch circuit can achieve bidirectional withstand voltage compensation for the RF switch branch, making the voltage swing of each stacked transistor uniform in both forward and reverse applications, thereby improving the total breakdown voltage of the RF switch circuit.

[0049] Figure 9 This is a schematic diagram of a standard transistor switching unit circuit designed using CMOS SOI technology according to an embodiment of the present invention.

[0050] refer to Figure 9The transistor switching unit circuit includes: a four-port NMOS transistor, a gate series resistor Rg, a source-drain series resistor Rds, and a body series resistor Rb. The transistor switching unit circuit has four ports: G, D, B, and S. The operating state of the transistor switching unit can be controlled by applying different control voltages to G and B. When the transistor switching unit is in the on state, for example, a 2.5V voltage (on-state voltage) can be applied to G, and a 0V voltage can be applied to B. A simplified equivalent circuit of the transistor switching unit in the on-state is shown below. Figure 10 As shown, it has a resistance Ron in the on-state, which is equivalent to the sum of the resistances between the D and S terminals. It should be understood that the parasitic capacitance and inductance of the transistor switching unit in the on-state are associated with existing switching unit circuits; however, since the parasitic capacitance and inductance in the on-state are relatively small, they are not... Figure 10 The diagram illustrates this. When the transistor switching unit is in the off state, for example, a -2.5V voltage (off voltage) can be applied to terminal G and a -2.5V voltage can be applied to terminal B. The simplified equivalent circuit of the transistor switching unit in the off state is shown below. Figure 11 As shown, it has a capacitance Coff in the off state. It should be understood that other parasitic capacitances and inductances of the transistor switching unit in the off state are associated with the existing switching unit circuit; however, since these other parasitic capacitances and inductances in the off state are relatively small, they are not... Figure 11 It is shown in the middle.

[0051] Table 1 illustrates the control logic of the radio frequency switch unit circuit according to an embodiment of the present invention. Referring to Table 1, the radio frequency switch unit circuit has three operating states: on state, isolation state 1, and isolation state 2. Although examples of control voltages of 2.5V (on voltage) and -2.5V (off voltage) are shown in Table 1, those skilled in the art should understand that the present invention is not limited to the above examples. Depending on different application scenarios, other control voltage values, such as 2V and -2V, can be used, and modifications and adjustments to the control voltage also fall within the protection scope of the present invention.

[0052] Table 1 does not list the control voltage for the body of the switching unit. Those skilled in the art will understand that the body control can be configured to vary with the gate control voltage. For example, when the transistor gate control voltage is 2.5V, the body control voltage is 0V; when the transistor gate control voltage is -2.5V, the body control voltage is -2.5V. According to embodiments of the present invention, the control voltages defined in Table 1 can be implemented using additional logic control circuitry, but the present invention does not limit this implementation.

[0053] Table 1

[0054]

[0055] Referring to Table 1, isolation state 1 is defined as the positive withstand voltage compensation state, that is, from Figure 8 The drain terminal (P1 port) of transistor M1 sees the RF swing of the antenna signal. According to the transistor operating states defined in Table 1, in isolation state 1, Figure 8 The equivalent circuit diagram of the RF switch unit circuit is as follows: Figure 12 As shown in (a) above. Transistor M1 is equivalent to capacitor C1, transistor M2A is equivalent to capacitor C2A, transistor M2B is equivalent to resistor R2B, transistor M3A is equivalent to resistor R3A, and transistor M3B is equivalent to capacitor C3B. Those skilled in the art will understand that other parasitic capacitances and inductances of the transistor switching unit in isolation state 1 are associated with existing switching unit circuits; however, because the other parasitic capacitances and inductances in the off state are relatively small, they are not... Figure 12 As shown in the diagram. Based on the principle of equivalent series-parallel impedance conversion, the series connection of C2A and R2B can be converted into a parallel connection of C2A and R2B_P. Similarly, the series connection of C3B and R3A can be converted into a parallel connection of C3B and R3A_P, as shown in the diagram. Figure 12 As shown in (b) of the diagram.

[0056] The following explanation uses a 65nm CMOS SOI process as an example. It is assumed that M1 is 5mm, M2A is 2mm, and M2B, M3A, and M3B are all 100µm in size. Those skilled in the art should understand that these values ​​can vary depending on the process, and this invention does not impose limitations. Based on the above limitations, C1 = 0.8pF, C2A = 0.33pF, C3B = 0.017pF, R2B = 5Ω, and R3A = 5Ω. At a frequency of 1GHz, the Q2 value of the series RC network composed of C2A and R2B is 96.6, and the Q3 value of the series RC network composed of C3B and R3A is 2000. Since the Q values ​​are very high, much greater than 10, the following formulas 5 and 6 can be derived based on the principle of equivalent series and parallel impedance interchange:

[0057] R2BP≈Q2 2 ×R²B=46kΩ (5)

[0058] R3AP≈Q2 2 ×R²B=20MΩ (6)

[0059] Through the Figure 12The capacitors and resistors in the equivalent circuit (b) are combined, and its equivalent circuit diagram is shown below. Figure 12 As shown in (c), where C4 = 0.347pF and R4 = 46KΩ, it can be seen that in isolation state 1, the equivalent capacitance and resistance values ​​of the RF switch unit circuit can be adjusted by adjusting transistor M2A.

[0060] Figure 13 This is a schematic diagram illustrating an application scenario of a radio frequency switching circuit according to an embodiment of the present invention. (Reference) Figure 13 Assume the signal source has a 50Ω load, the load is also a 50Ω system, and the RF signal is transmitted through a 50Ω RF transmission line system. When the RF switch unit circuit is in isolation state 1, since the RF system is a 50Ω transmission line system, the calculated impedance value of resistor R4 is much greater than 50Ω. R4 is a high impedance for a 50Ω RF transmission line system, therefore, it will not affect the transmitted signal. Resistor R4 can be further removed to simplify the equivalent circuit structure. The equivalent circuit of the RF switch unit circuit in isolation state 1 is capacitors C1 and C4 connected in parallel. Using the above-mentioned RF switch unit circuits stacked in series achieves a higher withstand voltage.

[0061] Figure 14 This is a schematic diagram illustrating the equivalent circuit of a two-stage stacked radio frequency switch circuit with forward withstand voltage compensation according to an embodiment of the present invention. Those skilled in the art should understand that... Figure 14 The invention is illustrated using a two-level stack as an example. However, it is not limited to a two-level stack and can be extended to an N-level stack, where N is a natural number greater than 1.

[0062] refer to Figure 14 Each RF switching unit circuit is in isolation state 1 and includes two capacitors, C1_x and C4_x, where x is the stage number, C1_x is the turn-off equivalent capacitor of transistor M1 in the first switching branch, and C4_x is the equivalent capacitor of the second and third switching branches in isolation state 1. The value of M2A_x can be adjusted through simulation design, and the value of C4_x can be further adjusted, i.e., Figure 14 The values ​​of C4_1 and C4_2 are used to further achieve positive uniform withstand voltage compensation for the two-stage stacked RF switch unit circuit.

[0063] The above analysis can be used as a reference to analyze the anti-voltage compensation state under isolation state 2. Figure 15 This is a schematic diagram illustrating the equivalent circuit of the reverse withstand voltage compensation for a two-stage stacked radio frequency switch circuit according to an embodiment of the present invention. Those skilled in the art should understand that... Figure 15 The invention is illustrated using a two-level stack as an example. However, it is not limited to a two-level stack and can be extended to an N-level stack, where N is a natural number greater than 1.

[0064] refer to Figure 15 Taking a 65nm CMOS SOI process as an example, M1 has a size of 5mm, M3A has a size of 2mm, and M2A, M2B, and M3B all have a size of 100um. Each stage of the RF switching unit circuit is in isolation state 2, and it contains two capacitors C1_x and C5_x, where x is the stage number, C1_x is the turn-off equivalent capacitor of the first switching branch transistor M1, and C5_x is the equivalent capacitor of the second and third switching branches in isolation state 2. Through simulation design, the value of M3A_x can be adjusted, and the value of C5_x can be further adjusted, that is, Figure 15 The values ​​of C5_1 and C5_2 in the code further enable reverse uniform withstand voltage compensation for the two-stage stacked RF switch unit circuit.

[0065] C4_x and C5_x are capacitors with different capacitance values. The capacitance value of each stage can be achieved by optimizing the values ​​of transistors M2A_x and M3A_x through simulation design. The RF switching circuit can compensate for the positive withstand voltage in isolation state 1 and for the negative withstand voltage in isolation state 2.

[0066] The control methods involved in the invention can be implemented by additional logic control circuits, such as by a switch controller. The present invention does not limit this and will not elaborate further here.

[0067] According to embodiments of the present invention, an N-stage stacked radio frequency (RF) switch circuit can be provided. The RF switch circuit according to embodiments of the present invention can perform bidirectional withstand voltage compensation for the RF switch branches and achieve uniform voltage division values ​​for each stage, thereby improving the total breakdown voltage of the RF switch circuit. The RF switch circuit according to embodiments of the present invention can be applied to 45V / 60V / 80V withstand voltage antenna tuning switch products.

[0068] Figure 17 This is a schematic diagram illustrating a radio frequency switching system according to an embodiment of the present invention. (Reference) Figure 17 The radio frequency (RF) switch system includes a switch controller 1701 and an RF switch circuit 1702. The RF switch circuit 1702 is formed by stacking the aforementioned N-level RF switch unit circuits in series, where N is an integer greater than 1. The switch controller 1701 is configured to provide control voltages to the transistors in the RF switch unit circuits to control the RF switch unit circuits to operate in an on-state, an isolation state 1, or an isolation state 2.

[0069] Although this disclosure has been described with reference to exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. This disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims.

[0070] Any description in this invention should not be construed as implying that any particular element, step, or function is essential and must be included within the scope of the claims. The scope of the patent subject matter is defined only by the claims.

Claims

1. A radio frequency switching circuit, comprising: A series of N RF switch units stacked together, where N is an integer greater than 1. The control circuit is configured to provide control voltage to the radio frequency switching unit circuit to put it into different operating states. The radio frequency (RF) switch unit circuit includes a first switch branch, a second switch branch, and a third switch branch connected in parallel. The first switch branch is configured as the main RF path, the second switch branch is configured as a forward withstand voltage compensation circuit, and the third switch branch is configured as a reverse withstand voltage compensation circuit. The first switching branch includes a first transistor, which is configured such that its gate is connected to a first control port of the RF switching unit circuit, its drain is connected to a first output port of the RF switching unit circuit, and its source is connected to a second output port of the RF switching unit circuit. The second switching branch includes a first compensation transistor and a first switching transistor, and The third switching branch includes a second compensation transistor and a second switching transistor. The control circuit is configured to control the radio frequency switch unit circuit to put it into an on state, a first isolation state, or a second isolation state.

2. The radio frequency switching circuit according to claim 1, wherein, The first compensation transistor is configured such that its gate is connected to the second control port of the radio frequency switching unit circuit, its drain is connected to the first output port of the radio frequency switching unit circuit, and its source is connected to the drain of the first switching transistor. The first switching transistor is configured such that its gate is connected to the third control port of the radio frequency switching unit circuit, and its source is connected to the second output port of the radio frequency switching unit circuit.

3. The radio frequency switching circuit according to claim 2, wherein, The size of the first compensation transistor is configured to be larger than the size of the first switching transistor.

4. The radio frequency switching circuit according to claim 1, wherein, The second compensation transistor is configured such that its gate is connected to the fourth control port of the radio frequency switching unit circuit, its drain is connected to the first output port of the radio frequency switching unit circuit, and its source is connected to the drain of the second switching transistor. The second switching transistor is configured such that its gate is connected to the fifth control port of the radio frequency switching unit circuit, and its source is connected to the second output port of the radio frequency switching unit circuit.

5. The radio frequency switching circuit according to claim 4, wherein, The size of the second compensation transistor is configured to be larger than the size of the second switching transistor.

6. The radio frequency switching circuit according to claim 1, wherein, In the on state, the control circuit provides an on-state voltage to the first transistor of the first switching branch; and provides an on-state voltage to the first compensation transistor and the first switching transistor of the second switching branch; And to provide turn-on voltage to the second compensation transistor and the second switching transistor of the third switching branch.

7. The radio frequency switching circuit according to claim 1, wherein, In the first isolation state, the control circuit provides a turn-off voltage to the first transistor of the first switching branch; and provides a turn-off voltage to the first compensation transistor of the second switching branch and a turn-on voltage to the first switching transistor. And to provide the turn-on voltage to the second compensation transistor of the third switching branch and the turn-off voltage to the second switching transistor.

8. The radio frequency switching circuit according to claim 1, wherein, In the second isolation state, the control circuit provides a turn-off voltage to the first transistor of the first switching branch; and provides a turn-on voltage to the first compensation transistor of the second switching branch and a turn-off voltage to the first switching transistor. And to provide a turn-off voltage to the second compensation transistor of the third switching branch and a turn-on voltage to the second switching transistor.

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